Download Digestive - Mrs. Kennedy`s Biology 11 Site!

Animal Digestion
Name, locate and describe the functions
of the parts of the digestive system.
Introduction
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Digestion is defined as the breakdown of
nutrients
We consume:
Proteins
Carbohydrates
Fats
Nucleic acids
These are broken down into their simplest
forms
And that’s not all…
We also consume:

Water – is not digested
1.
2.
Hydrates body’s cells
Enables transport and exchange of materials to and
from the cells
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3.
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Gases
Nutrients
Waste
Regulates body temperature
Vitamins
(living source)
/
/
Minerals
(non-living source)
*These are needed in trace amounts to assist reactions in the cells
From Beginning to End
Mouth
Esophagus
Stomach
Small intestine
Large intestine
Anus
Mouth
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Point at which ingestion takes place and
where food is chewed.
Site that begins mechanical and chemical
digestion of food

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Mechanical digestion = chewing
Chemical digestion = secretion of saliva
Teeth

provide mechanical
digestion of food by
breaking, cutting,
and tearing.

The increased
surface area :
aids in the
swallowing process.
 Allows more
efficient digestion
by chemicals.

Salivary Glands
Secrete saliva which:
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moistens the food (makes it slippery)
stimulates taste
Begins chemical digestion
Saliva contains the enzymes:
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salivary amylase
salivary maltase
*Enzymes are organic catalysts that
speed up chemical reactions
without being altered by the reaction.
Saliva includes:

Water: moistens consumed feed and aids in the
taste mechanisms.

Mucin: lubrication aid for swallowing.

Bicarbonate Salts: acts as a buffer to regulate
pH of the stomach.

Enzymes: salivary amylase/maltase initiates
carbohydrate breakdown.
Structures Beyond the Mouth…

Esophagus: hollow, muscular tube
that transports “bolus” from the
mouth to the stomach;
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Ingested material is moved by a
series of muscular contractions
referred to as peristaltic waves.
Cardiac Sphincter: valve at the
junction of the stomach and
esophagus.
Stomach: hollow, pear shaped,
muscular digestive organ
Functions of Stomach
(Site of Digestion)
Muscular movements cause
physical breakdown
by grinding food between folds
(called rugae).
Secretes digestive juices for
chemical breakdown:
1) Hydrochloric Acid
2) Pepsin
3) Rennin
Parts of the stomach:

Cardiac sphincterprevents backflow

Esophageal region:
non-glandular area
surrounding the cardiac
sphincter

Cardiac gland region:
contains cells that produce
primarily mucus (protects
stomach lining)

Fundic gland region: contains cells that
provide the gastric secretions needed for the
initial stages of digestion.
Parietal cells: produce hydrochloric acid.
 Chief cells: produce enzymes or precursors of
enzymes

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Pyloric gland region: contains cells that
produce mucus and some proteolytic
(protein digesting) enzymes.
Pylorus sphincter: at the beginning of the
small intestine which controls passage of
material (chyme) out of the stomach

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Stomach contents approximately a pH of 2
(kills bacteria).
Material arriving at the stomach is called the
bolus

Material leaving the stomach is called
chyme.
Just a Reminder…
Both types of digestion are
occurring in the stomach:
Mechanical and Chemical
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The churning of the stomach is considered
mechanical digestion
The enzyme activity is considered
chemical digestion
Chemical > Mechanical
Small Intestine - 3 sections
1.
Duodenum

(first section)
Receives secretions from:
 Pancreas: acts on proteins,
carbohydrates and lipids
 Liver: bile (stored in the
gallbladder) breaks down fat.
 Active site of digestion
2.
Jejunum: (middle section)
3.
Ileum: (last section)
active in nutrient absorption
active in nutrient absorption
Pancreas
Endocrine
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Insulin
glucagon
Exocrine
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Enzymes
(acini)
Bicarbonate
(ducts)
Small Intestine
Walls of the S.I. are lined
with a series of
fingerlike projections
called villi,
which in turn have
minute projections
called microvilli
that increase the
nutrient absorption
area.
Small intestine cont’d…
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Each nutrient has a specific absorption site.
Each villus contains an arteriole and venule,
together with a drainage tube of the
lymphatic system, a lacteal.
The venules ultimately drain into the portal
blood system, which goes directly to the
liver.

The lymph system empties via the thoracic
duct into the vena cava.
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S.I. contents are approximately pH 6 to 7.

Sight of digestion and absorption.
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Passive absorption = results from diffusion or
movement from high concentrations to low
concentrations.
Active absorption = transport of molecules
across the intestinal lining.
(villi) engulf the molecules and then actively
transport these molecules to either the bloodstream
or the lymph.
 Nutrients are carried to the liver where it is
detoxified.
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Large Intestine – 3 sections
1. Cecum (first sections)
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size varies considerably in different species;
Non-functional in humans (appendix)
Horses contain an active flora of bacteria similar to the
microbial population in rumen compartment of
ruminants.
 Bacterial breakdown of cellulose and other
carbohydrate material so the horse can utilize
fibrous feeds.
Site of bacterial synthesis of water-soluble
vitamins and protein.
2. Colon
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(middle section):
largest part of the large intestine
Primary area of water restoration from
intestinal contents.
3. Rectum
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(last section)
the end of the digestive tract before the
unabsorbed material (feces) is excreted out
the anus.
4. Anus:
•
external opening where unabsorbed materials
(feces) are expelled from the body.
Functions of the L.I.
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Site of water restoration
Secretion of some mineral elements
 calcium
Storage reservoir of undigested GI contents.
Bacterial fermentation:
 Synthesis of some water-soluble vitamins
and vitamin K.
 Some bacterial breakdown of fibrous
ingredients.
 Synthesis of some protein
Limited absorption of feedstuff from the L.I.
Cross-section of Digestive Tract
Defecation Reflex:
mass movement
 rectal distension
internal sphincter (invol)
 external sphincter (vol)
Bulk flow of liquid in gut
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Input
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Output
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Ingestion ~ 2 litres per day
Secretion (gut) ~ 7 litres/day
Faeces ~100 ml/day
Conclude ~ 9 litres/day absorbed
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Small intestine reabsorbs  7.5 L/day of water
Large Intestine reabsorbs 1.4 L/day
Digestive Health: Protection & Problems
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Immune defense: M-cells, Peyer's patches,
lymphocytes
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Irritable bowel disease – chronic
inflammation
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Diarrhea: leads to dehydration (4 million
deaths/yr)
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Vomiting (emesis) can lead to alkalosis
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Ulcers- H. pylori
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"heart-burn"  acid reflux disease
Summary
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Processes of digestion: ingestion, digestion,
absorption, secretion, motility, reabsorption
& defecation
Anatomy of digestion: mouth, esophagus,
stomach, small & large intestines, rectum,
anus (pancreas & liver)
Enzyme hydrolysis of carbohydrates, proteins,
lipids and nucleic acids provide the nutrients,
absorbed & conducted to liver for storage and
conversion
Some good websites
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http://kidshealth.org/kid/body/digest_noSW.ht
ml
http://www.teachnet.ie/farmnet/Digestive.htm
http://biology.clc.uc.edu/courses/bio105/digesti
v.htm
http://www.williamsclass.com/SeventhScience
Work/HumanBodySystemProject.htm